ADJUSTER GP-SEAT 3478750 - Caterpillar

MODIFICATION: For engines equipped with a damper adapter that has nine bolt holes, install a new adapter as shown in the chart. For engines equipped with a 6N7787 Adapter (which has twelve bolt holes), make a modification as follows: 1. Turn the engine crankshaft until the piston of number one cylinder is at the top dead center (TDC) position. See the topic "Finding Top Center Compression Position For Number One Piston" in the Service Manual.2. Remove any accessories or equipment (pulleys, sprockets, etc.) fastened to the 6N7787 Adapter.3. Remove the four 2D8426 Studs from the holes shown in the illustration. Be sure to remove the correct studs, as seen from the front of the engine.4. Install four 2D8155 Studs in these four holes only, and tighten to a torque of 54 6 N m (40 4 lb ft). The new 2D8155 Studs are 10.0 mm (.39") longer than the original 2D8426 Studs.5. During assembly, install twelve 5P8245 Washers (three on each stud) in addition to the original washers on the four new studs.6. Install any accessories or equipment (pulleys, sprockets, etc.) which were removed in Step 2. Tighten the stud nuts to a torque of 135 13 N m (100 10 lb ft).
The recommendation is to take vibration measurements after the modification is complete, for comparison with measurements taken before modification. This will give an indication of the amount of improvement. If the engine vibration is still not at an acceptable level, more assistance is available from the Service Engineering Department.
Front view of 6N7787 Adapter with engine No. 1 Cylinder at top dead center (TDC).